On 26.12.18 20:45, Jeff Liebermann wrote:> On Wed, 26 Dec 2018 11:01:56 -0500, bitrex <user@example.net> wrote: > >> Here's some interesting papers on sources of noise from small DC motors: >> <https://www.mdpi.com/2072-666X/9/2/84/pdf> >> <http://downloads.hindawi.com/journals/ijrm/2006/063214.pdf> >> The first seems to indicate a significant source of noise at high freq >> in small motors is excited resonance of the motor housing itself > > Suggestion: Remove the propellers from the quadcopter and run the > motors without the props. The residual noise should be 100% chopper > noise. I did that in the past on my Walkera XR-350 clone: > <http://www.learnbydestroying.com/jeffl/pics/drivel/slides/Walkera%20QR%20X350%20Drone.html> > and heard very little remaining noise from the motors. However, my > hearing is not the best, and I didn't bother making any measurements > with an SPL meter. If I find time, I might try it again later today.If you remove the propellers, you should substitute a comparable amount of torque load to keep the operating conditions. The noise will be significantly lower when there is no torque load. -- -TV
How to stop electrical whining noise?
Started by ●December 26, 2018
Reply by ●December 26, 20182018-12-26
Reply by ●December 26, 20182018-12-26
tabbypurr@gmail.com wrote:> bitrex wrote: >> Klaus Kragelund wrote:>>> It sounds to me like it is switching noise from the motor drive, >>> which causes movement of the motor windings >>> >>> It sounds to be a steady noise frequency which it won't be if >>> it is related to the blades. No way to change it, except to >>> change the motor control SW or filter the output to the motor to >>> reduce the switching current ripple>> if it's electrically excited/resonant acoustic noise caused by a >> specific PWM harmonic in the audible range (the whine seems to be >> consistent in frequency across the motor power output range) what >> about a parallel-series LC band-reject in the PWM drive output to >> the motors? > >> The armature can't resonate at that frequency if it can't get any >> power from the controller at that frequency > > The whining noise is clearly constant frequency as the motors pick > up speed, and can't possibly be produced by the propellors. There > are 2 solutions: > 1. move to an ultrasonic switching frequency > 2. Infiltrate varnish etc into the switched mode inductor & put foam > under the PCB it's on.There is no such sound on most other drones.
Reply by ●December 26, 20182018-12-26
On Wed, 26 Dec 2018 21:43:53 +0200, Tauno Voipio <tauno.voipio@notused.fi.invalid> wrote:>On 26.12.18 20:45, Jeff Liebermann wrote: >> On Wed, 26 Dec 2018 11:01:56 -0500, bitrex <user@example.net> wrote: >> >>> Here's some interesting papers on sources of noise from small DC motors: >>> <https://www.mdpi.com/2072-666X/9/2/84/pdf> >>> <http://downloads.hindawi.com/journals/ijrm/2006/063214.pdf> >>> The first seems to indicate a significant source of noise at high freq >>> in small motors is excited resonance of the motor housing itself >> >> Suggestion: Remove the propellers from the quadcopter and run the >> motors without the props. The residual noise should be 100% chopper >> noise. I did that in the past on my Walkera XR-350 clone: >> <http://www.learnbydestroying.com/jeffl/pics/drivel/slides/Walkera%20QR%20X350%20Drone.html> >> and heard very little remaining noise from the motors. However, my >> hearing is not the best, and I didn't bother making any measurements >> with an SPL meter. If I find time, I might try it again later today.>If you remove the propellers, you should substitute a >comparable amount of torque load to keep the operating >conditions. The noise will be significantly lower when >there is no torque load.I could do that using a disk (washer) with a radius of about 30% of the propeller radius (center of mass) and having the same weight as the four propellers. I think I have some spare props left over from my last attempt at indoor flying (before I added the shrouds). It's not a good equivalent load torque because it's not pushing air, but methinks the inertial load of the disk (washer) will be sufficient to have the chopper produce some vibrations. However, I won't have time for a few days. The doctors will be removing two large kidney stones tomorrow and I may need some time to recover. To be continued when possible. -- Jeff Liebermann jeffl@cruzio.com 150 Felker St #D http://www.LearnByDestroying.com Santa Cruz CA 95060 http://802.11junk.com Skype: JeffLiebermann AE6KS 831-336-2558
Reply by ●December 26, 20182018-12-26
On Wed, 26 Dec 2018 07:51:31 -0000 (UTC), John Doe <always.look@message.header> wrote:>bitrex <user@example.net> wrote: > >> Klaus Kragelund wrote: > >>> It sounds to me like it is switching noise from the motor drive, >>> which causes movement of the motor windings >>> >>> It sounds to be a steady noise frequency which it won’t be if >>> it is related to the blades >>> >>> No way to change it, except to change the motor control SW or >>> filter the output to the motor to reduce the switching current >>> ripple > >> I hear it now. Had to put on headphones, on laptop speakers I only >> hear the lower pitched blade noise>I was just coming back to post about that possibility. The frequency >is at least 8 kHz. A bad sound system or failing ears might not even >know what sound we're talking about.<https://www.youtube.com/watch?v=FSwZQtqWyHw> Audio spectrum from the YouTube video: <http://www.learnbydestroying.com/jeffl/crud/drone-noise-spectrum-01.jpg> Peaks at 300Hz, it's harmonics, and chopper noise at about 8KHz. However, the rather high broadband audio noise level is quite real. Removing the 300 and 8000Hz tones would probably not have much of an effect on the overall noise level, which would still sound like white noise air turbulence, similar to the noise from a compressed air nozzle. -- Jeff Liebermann jeffl@cruzio.com 150 Felker St #D http://www.LearnByDestroying.com Santa Cruz CA 95060 http://802.11junk.com Skype: JeffLiebermann AE6KS 831-336-2558
Reply by ●December 26, 20182018-12-26
Jeff Liebermann <jeffl@cruzio.com> wrote:> John Doe <always.look@message.header> wrote: >> bitrex <user@example.net> wrote: >>> Klaus Kragelund wrote: >> >>>> It sounds to me like it is switching noise from the motor >>>> drive, which causes movement of the motor windings >>>> >>>> It sounds to be a steady noise frequency which it won’t be if >>>> it is related to the blades >>>> >>>> No way to change it, except to change the motor control SW or >>>> filter the output to the motor to reduce the switching current >>>> ripple >> >>> I hear it now. Had to put on headphones, on laptop speakers I >>> only hear the lower pitched blade noise > >> I was just coming back to post about that possibility. The >> frequency is at least 8 kHz. A bad sound system or failing ears >> might not even know what sound we're talking about. > > <https://www.youtube.com/watch?v=FSwZQtqWyHw>> <http://www.learnbydestroying.com/jeffl/crud/drone-noise-spectrum-01.jpg>> Removing the 300 and 8000Hz tones would probably not have much of > an effect on the overall noise levelMaybe because you can't hear it. It makes a big difference to me. Shown by pulling my 8 kHz equalizer slider down to zero. You say "I never guess". You might want to start. Even Blinkin was guessing, and he could at least hear... https://youtu.be/zJQ7FxLzhVs
Reply by ●December 26, 20182018-12-26
On 12/26/18 7:51 PM, Jeff Liebermann wrote:> On Wed, 26 Dec 2018 21:43:53 +0200, Tauno Voipio > <tauno.voipio@notused.fi.invalid> wrote: > >> On 26.12.18 20:45, Jeff Liebermann wrote: >>> On Wed, 26 Dec 2018 11:01:56 -0500, bitrex <user@example.net> wrote: >>> >>>> Here's some interesting papers on sources of noise from small DC motors: >>>> <https://www.mdpi.com/2072-666X/9/2/84/pdf> >>>> <http://downloads.hindawi.com/journals/ijrm/2006/063214.pdf> >>>> The first seems to indicate a significant source of noise at high freq >>>> in small motors is excited resonance of the motor housing itself >>> >>> Suggestion: Remove the propellers from the quadcopter and run the >>> motors without the props. The residual noise should be 100% chopper >>> noise. I did that in the past on my Walkera XR-350 clone: >>> <http://www.learnbydestroying.com/jeffl/pics/drivel/slides/Walkera%20QR%20X350%20Drone.html> >>> and heard very little remaining noise from the motors. However, my >>> hearing is not the best, and I didn't bother making any measurements >>> with an SPL meter. If I find time, I might try it again later today. > >> If you remove the propellers, you should substitute a >> comparable amount of torque load to keep the operating >> conditions. The noise will be significantly lower when >> there is no torque load. > > I could do that using a disk (washer) with a radius of about 30% of > the propeller radius (center of mass) and having the same weight as > the four propellers. I think I have some spare props left over from > my last attempt at indoor flying (before I added the shrouds). It's > not a good equivalent load torque because it's not pushing air, but > methinks the inertial load of the disk (washer) will be sufficient to > have the chopper produce some vibrations. > > However, I won't have time for a few days. The doctors will be > removing two large kidney stones tomorrow and I may need some time to > recover. To be continued when possible. > > >Yikes. Best wishes for a speedy recovery--I'll pray for you. Cheers Phil Hobbs -- Dr Philip C D Hobbs Principal Consultant ElectroOptical Innovations LLC / Hobbs ElectroOptics Optics, Electro-optics, Photonics, Analog Electronics Briarcliff Manor NY 10510 http://electrooptical.net http://hobbs-eo.com
Reply by ●December 27, 20182018-12-27
On Thu, 27 Dec 2018 02:28:58 -0000 (UTC), John Doe <always.look@message.header> wrote:>Jeff Liebermann <jeffl@cruzio.com> wrote: >> Removing the 300 and 8000Hz tones would probably not have much of >> an effect on the overall noise level>Maybe because you can't hear it. It makes a big difference to me. >Shown by pulling my 8 kHz equalizer slider down to zero.It's possible that I can't hear 8KHz. I haven't tested my hearing in the last 5 years or so.>You say "I never guess".Close. I said: "I never guess when I can also test". In other words, if there's a way to test my assertions, I prefer doing that instead of guessing. If that fails, use "the force". Actually, I do quite a bit of guessing, far more than I consider acceptable. My favorite excuse is lack of time, which I shall now invoke as my reason for not testing my hearing or manipulating the audio track. Besides, it's your problem, not mine, so you should be doing the experimentation.>You might want to start. >Even Blinkin was guessing, and he could at least hear... >https://youtu.be/zJQ7FxLzhVsTake the recording from the YouTube video and notch out the 8KHz. Audacity should be suitable for the task: <https://manual.audacityteam.org/man/notch_filter.html> Does it now sound acceptable? If so, build a hearing aid or mechanical headset with a built in 8KHz notch filter, which should help you fly without irritating noises. Hmmm... I smell a product idea. -- Jeff Liebermann jeffl@cruzio.com 150 Felker St #D http://www.LearnByDestroying.com Santa Cruz CA 95060 http://802.11junk.com Skype: JeffLiebermann AE6KS 831-336-2558
Reply by ●December 27, 20182018-12-27
If the switching frequency is 8kHz, there is of course also harmonics and subharmonics, so just removing the 8kHz from the recording is not a representative figure Cheers Klaus
Reply by ●December 28, 20182018-12-28
On Wed, 26 Dec 2018 22:26:18 -0500, Phil Hobbs <pcdhSpamMeSenseless@electrooptical.net> wrote:>On 12/26/18 7:51 PM, Jeff Liebermann wrote:>> However, I won't have time for a few days. The doctors will be >> removing two large kidney stones tomorrow and I may need some time to >> recover. To be continued when possible.>Yikes. Best wishes for a speedy recovery--I'll pray for you. >Cheers >Phil HobbsThank you. I could use all the help I can get. I survived. Left stone is gone. Right stone is split into tiny rubble, and should pass when the urologist removes the stents in a week. It's now 4AM on the left coast and I can't sleep due to pain and having constantly run to the bathroom. That should diminish sometime tomorrow. I'll eventually be back to normal, except for my contribution to the doctor, hospital, anesthesiologist, etc bills. My apologies for the off topic topic, but it's literally all I can think of at this time. -- Jeff Liebermann jeffl@cruzio.com 150 Felker St #D http://www.LearnByDestroying.com Santa Cruz CA 95060 http://802.11junk.com Skype: JeffLiebermann AE6KS 831-336-2558
Reply by ●December 28, 20182018-12-28
On 2018-12-26, Tauno Voipio <tauno.voipio@notused.fi.invalid> wrote:> On 26.12.18 20:45, Jeff Liebermann wrote: >> On Wed, 26 Dec 2018 11:01:56 -0500, bitrex <user@example.net> wrote: >> >>> Here's some interesting papers on sources of noise from small DC motors: >>> <https://www.mdpi.com/2072-666X/9/2/84/pdf> >>> <http://downloads.hindawi.com/journals/ijrm/2006/063214.pdf> >>> The first seems to indicate a significant source of noise at high freq >>> in small motors is excited resonance of the motor housing itself >> >> Suggestion: Remove the propellers from the quadcopter and run the >> motors without the props. The residual noise should be 100% chopper >> noise. I did that in the past on my Walkera XR-350 clone: >> <http://www.learnbydestroying.com/jeffl/pics/drivel/slides/Walkera%20QR%20X350%20Drone.html> >> and heard very little remaining noise from the motors. However, my >> hearing is not the best, and I didn't bother making any measurements >> with an SPL meter. If I find time, I might try it again later today. > > > If you remove the propellers, you should substitute a > comparable amount of torque load to keep the operating > conditions. The noise will be significantly lower when > there is no torque load.yes, EG. fit an aluminium flywheel with a magnetic brake, or some other near-silent mechanical load -- When I tried casting out nines I made a hash of it.
